Methods and Apparatus For Reducing the Noise Level Outputted by Oil Separator

ABSTRACT

A muffling apparatus ( 100 ) having a first, muffling segment ( 1010 ) and a second ( 1020 ), non-muffling segment is provided for placement within an oil separator of refrigeration or cooling system, wherein the apparatus has a non-straight shape and a lumen defined therein to allow for noise-creating pressure pulsations/waves to come into contact with absorbing material ( 120 ) of the muffling segment ( 1010 ) in order to attenuate the energy of the pressure waves/pulsations into heat and thus reduce oil separator vibrations caused thereby.

FIELD OF THE INVENTION

This invention relates to oil separators for use in refrigeration andcooling systems, and, in particular, to methods and apparatus forreducing the noise levels outputted by an oil separator that is locatedwithin a refrigeration or cooling system.

BACKGROUND OF THE INVENTION

As illustrated by FIG. 1, a water cooled chiller type refrigerationsystem 10 using a screw compressor 20 typically includes a condenser 30,a cooler 40, an oil separator 50, a condenser fan 60 and one or moreexpansion devices 70. The compressor 20 requires oil for lubrication,wherein the oil is typically entrained in a refrigerant. The combinedoil and refrigerant mixture is carried through a compression cycle anddischarged into the oil separator 50, where the oil must be removed fromthe refrigerant to allow for proper operation of the cooler 40. From theoil separator 50, the clean refrigerant flows to the condenser 30 andthe separated oil is returned to the compressor 10.

Most known oil separators, such as those described in U.S. Pat. No.5,704,215 to Lord et al. (the entirety of which is incorporated byreference herein), perform this separation function well. However, ithas been observed that high noise levels are often generated in thevicinity of an oil separator 50 within a refrigeration system, such asthe system 100 illustrated in FIG. 1. Without wishing to be bound bytheory, it is believed that this is caused by high level pressurewaves/pulsations (i.e., 250 Hz or above) emanating from the compressor20 that are transferred to the oil separator 50, which acts like aresonant cavity and thus is excited by the compressor pulsations. Thisexcitement causes high vibration levels at the surface of the oilseparator 50, and that, in turn, translates into high noise levelsoutputted by the oil separator. These excess noise levels can bedistracting and bothersome, or, even worse, can be damaging to thehearing of those working around the oil separator 50 and/or can be inviolation of applicable noise ordinances.

Previous efforts by those in the art to reduce the high noise levelsproduced by an oil separator 50 have focused on placing noise reductionequipment or devices between the oil separator and the compressor 20.Often, however, such equipment is subjected to high pressuredifferentials between the compressor discharge within the equipment andthe atmosphere outside of the equipment. In such instances, the noisereduction equipment functions, in essence, as a pressure vessel, thusimplicating strict design rules, certifications, and by consequence,added costs. Moreover, the added noise reduction equipment causes therefrigeration/cooling system to occupy a larger overall footprint, whichis suboptimal and can even outweigh any beneficial noise reduction thatactually is achieved through use of the equipment.

Therefore, a need exists for methods and apparatus to reduce the noiseoutput of an oil separator without interfering with the functioning ofthe oil separator or any other equipment utilized in connection with therefrigeration system, and wherein such methods and apparatus would notbe plagued by any of the various drawbacks associated with mufflingapparatus known in the art.

SUMMARY OF THE INVENTION

These and other needs are met by the present invention, which provides amuffling apparatus and methods for using the muffling apparatus toreduce the noise level output of an oil separator within a refrigerationor cooling system. The muffling apparatus of the present invention has afirst, muffling segment and a second, non-muffling segment and is placedwithin an internal area of an oil separator.

The muffling segment of the muffling apparatus is at least partiallyformed of an absorbing material. The absorbing material is effective toattenuate the energy of pressure waves/pulsations from the compressorinto heat, thus reducing the resultant vibrations of (and, in turn,noise levels outputted from) the oil separator caused by energy from thewaves/pulsations. The muffling segment is comprised of a tubular bodythat includes an external shell, wherein the external shell surrounds aninternal layer and wherein the internal layer surrounds an internalshell. The muffling segment also has a first end, a second end and alumen therebetween, wherein the lumen is surrounded by the internalshell of the muffling segment.

In an exemplary aspect of the present invention, the internal layer ofthe muffling segment of the muffling apparatus is made of the absorbingmaterial, and the internal shell has a plurality ofperforations/openings defined therein. Each opening provides a directfluid/air pathway from the lumen to the internal layer of absorbingmaterial. The purpose of the openings is to enable the pressurewaves/pulsations that propagate through the lumen of the mufflingsegment to come into contact with the internal layer of absorbingmaterial, thus enabling the absorbing material to attenuate the pressurewaves/pulsations.

In another exemplary aspect of the present invention, the non-mufflingsegment of the muffling apparatus has a tubular body, wherein the firstend of the non-muffling segment is connected to the second end of themuffling segment and the second end of the non-muffling segment isconnected to an internal area of an oil separator.

In yet another exemplary aspect of the present invention, the mufflingapparatus has a non-straight shape, such as a bent shape or a curvedshape, wherein the bent or curved portion(s) of the non-straightmuffling apparatus are part of the non-muffling segment.

Still other aspects, embodiments and advantages of the present inventionare discussed in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and desired objects of thepresent invention, reference is made to the following detaileddescription taken in conjunction with the accompanying figures, whereinlike reference characters denote corresponding parts throughout theviews, and in which:

FIG. 1 is a schematic view of a known exemplary arrangement of arefrigeration/cooling system utilizing an oil separator.

FIG. 2 is a perspective view of an exemplary embodiment of an oilseparator muffling apparatus in accordance with the present invention;

FIG. 3 is a side, cross-sectional view of the muffling apparatus of FIG.2 taken along line 3-3 of FIG. 2; and

FIG. 4 is a perspective view, with partial cut away, of an exemplary oilseparator wherein the muffling apparatus of FIGS. 2 and 3 has beenplaced within an internal area thereof.

DETAILED DESCRIPTION

The present invention provides a muffling apparatus and methods of usingthe apparatus to reduce the noise level output produced by an oilseparator of a refrigeration or cooling system, such as a water-cooledchiller type refrigeration system. In use, the muffling apparatus of thepresent invention is placed within an oil separator in order toattenuate pressure waves/pulsations that emanate from the compressor ofthe refrigeration system. As discussed above, such pressurewaves/pulsations are believed to be responsible for creating vibrationalforces that cause the oil separator surface to vibrate and, in turn, todisadvantageously generate high noise levels in its vicinity.

Attenuation occurs during use of the muffling apparatus of the presentinvention because the pressure waves/pulsations come into contact withan absorbing material located within a muffling segment of the mufflingapparatus. The absorbing material attenuates the energy of the pressurewaves/pulsations into heat and thus reduces the resultant vibrations of(and, in turn, noise levels outputted from) the oil separator that arecaused by energy from the pressure waves/pulsations.

The muffling apparatus of the present invention has many benefits. Inparticular, not only does the muffling apparatus successfully reduce oilseparator noise levels, but it does so while being sited within an oilseparator, thus not requiring the refrigeration/cooling system to occupyadded space and not exposing the muffling apparatus to high pressuredifferentials. The design of the muffling apparatus also provides costssavings, as will be discussed in detail below.

FIGS. 2 and 3 depict an exemplary oil separator muffling apparatus 100in accordance with the present invention. The muffling apparatus 100 hasat least two segments, wherein each segment serves a different purposein accordance with the present invention and is made of differentmaterials or material combinations than the other segment(s). Thesegments are connected to each other as is known in the art, e.g., bywelding, brazing and/or through the use of rivets.

As is currently preferred, and as is best shown in FIG. 3, a mufflingapparatus 100 of the present invention has a first, muffling segment1010 and a second, non-muffling segment 1020. The muffling segment 1010has a tubular body comprised of an external shell 110 that surrounds aninternal layer 120, wherein the internal layer has an internal shell130—that is, the external shell and the internal shell “sandwich” theinternal layer. Although it is currently preferred for the number andarrangement of the shells 110, 130 and the internal layer 120 of themuffling segment 1010 to be as shown in FIGS. 2 and 3, it is also withinthe scope of the present invention for the muffling segment to becomprised of more or fewer layers and/or more or fewer shells than aredepicted in the Figures, and/or for the layer(s) and/or the shell(s) tohave a different arrangement than that which is shown.

The muffling segment 1010 has a first end 140, a second end 150 and alumen 160 therebetween, wherein the lumen is surrounded by the internalshell 130. The second end 150 of the muffling segment 1010 is adaptedfor connection to a first end 1100 of the non-muffling segment 1020 bytechniques known in the art, e.g., welding, brazing and/or through theuse of rivets.

As noted above, the purpose of the muffling segment 1010 is to reducethe noise level output of an oil separator in which the mufflingapparatus 100 is placed. To enable that to occur, at least one of theexternal shell 110, the internal layer 120 and the internal shell 130 ofthe muffling segment 1010 should be made, at least partially, of amaterial that will absorb the energy from pressure waves (that emanatefrom the compressor and are transferred to the oil separator) anddissipate/attenuate that energy into absorbable heat. According to acurrently preferred embodiment of the present invention, the internallayer 120 of the muffling segment 1010 is made of such an absorbingmaterial. The specific choice of the absorbing material can varyaccording to several factors, including but not limited to cost, dumpingcharacteristics, availability and designer preference. According to anexemplary embodiment of the present invention, the absorbing material isa fiberglass material. A currently preferred fiberglass material iscomprised of glass fibers with a phenolic resin, wherein the materialhas a density in the range of about 86 kg/m³ to about 105 kg/m³ and amaximum temperature of about 177° C.

The material(s) from which the external shell 110 and the internal shell130 of the muffling segment 1010 are constructed should be strong anddurable, yet inexpensive. The external shell 110 and the internal shell130 can be constructed of different or identical materials; however,according to an exemplary embodiment of the present invention, both theexternal shell 110 and the internal shell 130 are constructed of a sheetmetal material. A currently preferred sheet metal material is steel, butother metal-based materials can be utilized as well.

As shown in FIGS. 2 and 3, the internal shell 130 of the mufflingsegment 1010 has a plurality of perforations or openings 170 definedtherein. Each opening 170 provides direct fluid communication betweenthe lumen 160 and the internal layer 120 of absorbing material. Thepurpose of the openings 170 is to enable the pressure waves/pulsationsthat are propagating/passing through the lumen 160 of the mufflingsegment 1010 to come into contact with the internal layer 120 ofabsorbing material, thus enabling the absorbing material to attenuatethe pressure waves/pulsations.

The size, shape, number and spacing interval of the openings 170 canvary depending on several factors, including, but not limited to, thefrequency of the pressure waves/pulsations that are expected to beencountered. According to a currently preferred embodiment of thepresent invention, openings 170 are defined in a range of about 10% toabout 50% of the overall surface area of the internal shell 130.Moreover, although the openings 170 can have any shape and any spacinginterval, it is currently preferred for the openings to be substantiallyround and spaced apart from each other at substantially identicaldistances, as best shown in FIG. 3.

The non-muffling segment 1020 of the muffling apparatus 100 also has atubular body, and has first and second ends 1100, 1200. The first end1100 of the non-muffling segment is connected to the second end 150 ofthe muffling segment 1010, and the second end 1200 of the mufflingsegment is connected to an internal area 510 of an oil separator 500, asshown in FIG. 4. Such connections are made as is generally known in theart, e.g., via welding, brazing and/or through the use of rivets.

Although the non-muffling segment 1020 of the muffling apparatus 100 canhave more than one layer and can be made of more than one material, itis currently preferred to form the non-muffling segment of one layer andone material, wherein suitable materials include sheet metal materialssuch as steel. There are several advantages of forming the non-mufflingsegment 1020 of the muffling apparatus entirely from a metal-basedmaterial, including, but not limited to, cost savings and designflexibility. The cost savings occurs because sheet metal material isless expensive to purchase as compared to the absorbing material used inthe muffling segment 1010. Also, there is design flexibility because onecan purchase many different pre-formed shapes and sizes of the sheetmetal material from which the non-muffling segment 1020 is formed.

The size and shape of muffling apparatus 100 also can vary; however, itis currently preferred for muffling apparatus 100 to have a non-straightoverall shape. For example, FIGS. 2 and 3 depict a muffling apparatusthat has a curved shape. The non-straight shape of muffling apparatus100 is preferred because it enables the apparatus to have a larger size(as compared to an apparatus with a straight shape) while still fittingwithin the space confines of an oil separator. That allows for a longerlumen 160 to be defined between the first and second ends 140, 150 of athe muffling segment 1010, thus providing added opportunities forpressure waves/pulsations to come into contact with the internal layer120 via openings 170.

As shown in FIGS. 2 and 3, and as is currently preferred, mufflingsegment 1010 of muffling apparatus 100 has a substantially straightshape and non-muffling segment 1020 has a curved shape. Such anarrangement is advantageous because a cost savings is achieved by notforming the muffling apparatus entirely of the muffling segmentmaterials, yet the muffling apparatus is still capable of providingsignificant noise reduction, as will be discussed in more detail below.

Optionally, and as shown in the Figures, support element 600 is attached(e.g., by welding) to the first end 150 of the muffling segment 1010 andto the internal area 510 of the oil separator 500. The presence of thesupport element 600 provides added support to muffling apparatus 100 bybearing the weight of muffling segment 1010. Support element 600 can bemade of a variety of materials, including, but not limited, to one ormore metal-based materials (e.g., steel).

The size of the muffling apparatus 100 can vary depending on severalfactors, most notably the size of the oil separator in which themuffling apparatus is installed. It is currently preferred for the sizeof the muffling apparatus 100 to vary proportionally with the size ofthe oil separator. For example, the muffling apparatus 100 will have adifferent predetermined size in order to fit within a 14 inch oilseparator than it would to fit within a 16 inch oil separator or an 18inch oil separator, wherein the size of the muffling apparatus for a 16inch oil separator generally will be approximately 16/14 times the sizeof the muffling apparatus for a 14 inch oil separator and approximately16/18 times the size of the muffling apparatus for an 18 inch oilseparator.

According to an exemplary embodiment of the present invention in whichthe muffling apparatus 100 is placed in a 14 inch oil separator, theeffective height, H (see FIG. 3), occupied by the muffling apparatus isin the range of about 7.5 inches to about 9.5 inches, with an effectiveheight of about 8.5 inches being currently preferred, and the effectivelength, L (see FIG. 3) occupied by the muffling apparatus is in therange of about 11 inches to about 13.5 inches, with an effective heightof about 13.2 inches being currently preferred. For placement within a16 inch oil separator, these measurements would be approximately 16/14times those for the 14 inch oil separator, and for placement within an18 inch oil separator, they would be approximately 18/14 times those forthe 14 inch oil separator.

The length of muffling segment 1010 also can vary according to severalfactors, including the frequency of the pressure waves expected to theencountered within the oil separator. For example, the length ofmuffling segment 1010 can be comparatively greater when the frequency ofthe pressure waves is expected to be about 2000 Hz versus 125 Hz.According to an exemplary embodiment of the present invention in whichmuffling apparatus 100 is placed within a 14 inch oil separator, thelength of the muffling segment 1010 is about 4.5 inches to about 6.5inches, wherein a length of about 6 inches is currently preferred.Stated differently, the length of muffling segment 1010 generallycomprises about 30% to about 60% of the overall length, L, of themuffling apparatus 100. For placement within a 16 inch and 18 inch oilseparators, the length measurements would be approximately 16/14 timesgreater and 18/14 times greater, respectively.

Experiments were conducted to assess the noise reduction efficacy of amuffling apparatus 100 of the present invention. The experiments wereperformed in accordance with the guidelines of InternationalOrganization for Standardization (ISO 9614). The results of theexperiments are shown in Table I below:

TABLE I Pressure Wave (octave in Hz) 125 250 500 1000 2000 4000 Acousticchange (dB) due to −1 −12 −6 −1 −7 −12 presence of muffling apparatusGlobal dBA = −4

To accumulate the test results in Table I, a refrigeration system wasfirst operated such that its oil separator encountered six differentpressure wave frequencies (125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and4000 Hz) emanating from its compressor, wherein the noise leveloutputted by the oil separator in response to each of these pressurewave levels was measured and recorded. A muffling apparatus 100 of thetype shown in FIGS. 2 and 3 was then installed within the oil separatorand the testing conditions were repeated to gather comparable data.

The experimental results in Table I demonstrate that there was anacoustic reduction at each pressure wave frequency level due to thepresence of the muffling apparatus 100, wherein the acoustic reductionwas calculated as the difference between the acoustic level at the oilseparator without a muffling apparatus versus the acoustic level at thesame oil separator with a muffling apparatus of the present inventioninstalled within an internal area thereof. Therefore, the −12 dBmeasurement at 250 Hz indicates that the noise level measurement takenafter the muffling apparatus 100 was installed within the oil separatorwas 12 dB less than the measurement taken when the same oil separatorwas not equipped with the muffling apparatus. The Global dBA of −4 dBAalso supports that there was an acoustic reduction, and that thedominant frequency band of the pressure waves/pulsations was in therange of about 500-1000 Hz.

The results in Table I are very favorable. In particular, noisereduction levels were observed for each of the six selected pressurewave frequency bands. This is important because different compressorsoperate at different dominant pressure output levels, and thus wouldproduce different Global dBA measurements. Moreover, noise reductionoccurred despite the fact that the muffling apparatus was only partiallyformed of a muffling segment 1010. This signifies that by forming themuffling apparatus from a muffling segment 1010 and a non-mufflingsegment 1020, one can achieve noise reduction while enjoying costsavings and design flexibility.

Thus, a muffling apparatus 100 of the type shown in FIGS. 2 and 3 can beinstalled in an oil separator with confidence that the noise levelreduction will be at least 1 dB, with a noise reduction level of up to12 dB being possible as well depending on the dominant frequency band ofthe pressure/wave pulsations emanating from the compressor. These aresignificant noise reduction levels, especially when considering theeffects of exposure to the reduced noise level over the lifetime of therefrigeration system in which the oil separator is located. Moreover, anoise reduction level of between 1 dB and 12 dB will be even moresignificant if, as is commonly the case, multiple refrigeration systemsthat include oil separators are installed in close proximity.

Although the present invention has been described herein with referenceto details of currently preferred embodiments, it is not intended thatsuch details be regarded as limiting the scope of the invention, exceptas and to the extent that they are included in the following claims—thatis, the foregoing description of the present invention is merelyillustrative, and it should be understood that variations andmodifications can be effected without departing from the scope or spiritof the invention as set forth in the following claims. Moreover, anydocument(s) mentioned herein are incorporated by reference in theirentirety, as are any other documents that are referenced within thedocument(s) mentioned herein.

1. A method for reducing the noise level outputted by an oil separator within a refrigeration or cooling system, comprising the steps of: providing a muffling apparatus having a first segment and a second segment, wherein the first segment includes an absorbing material; and placing the muffling apparatus within an internal area of an oil separator.
 2. The method of claim 1, wherein the muffling apparatus has a non-straight overall shape.
 3. The method of claim 2, wherein the non-straight overall shape is selected from the group consisting of a bent shape and a curved shape.
 4. The method of claim 2, wherein the first segment has a substantially straight shape and the second segment has a substantially curved shape.
 5. The method of claim 1, wherein the first segment has a first end, a second end and a lumen defined therebetween, and wherein at least a portion of the absorbing material is in direct fluid communication with the lumen.
 6. The method of claim 5, wherein at least a portion of the absorbing material is in direct fluid communication with the lumen via a plurality of openings.
 7. The method of claim 1, wherein the step of placing the muffling apparatus within the internal area of the oil separator is accomplished by attaching the muffling apparatus to the internal area of the oil separator.
 8. The method of claim 1, wherein the muffling apparatus is attached to a first end of a support element, and wherein a second end of the support element is attached to the internal area of the oil separator.
 9. The method of claim 1, wherein the absorbing material is a fiberglass material.
 10. A muffling apparatus for placement within an internal area of an oil separator, the muffling apparatus comprising: a first segment having a first end, a second end and a lumen therebetween, wherein the first segment is at least partially constructed of an absorbing material; and a second segment connected to the first segment.
 11. The muffling apparatus of claim 10, wherein at least a portion of the absorbing material is in direct fluid communication with the lumen.
 12. The muffling apparatus of claim 10, wherein the first segment is comprised of: an external shell; an internal layer formed at least partially of the absorbing material, wherein the internal layer is surrounded by the external shell; and an internal shell, wherein the internal shell surrounds the lumen.
 13. The muffling apparatus of claim 12, wherein the internal layer has a plurality of openings defined therein to enable direct fluid communication between the absorbing material and the lumen.
 14. The muffling apparatus of claim 10, wherein the absorbing material is a fiberglass material.
 15. The muffling apparatus of claim 12, wherein each of the external shell and the internal shell is made of a sheet metal material.
 16. The muffling apparatus of claim 11, wherein the muffling apparatus has a non-straight overall shape.
 17. The muffling apparatus of claim 16, wherein the non-straight overall shape is selected from the group consisting of a bent shape and a curved shape.
 18. The muffling apparatus of claim 16, wherein the first segment has a substantially straight shape and the second segment has a substantially curved shape
 19. The muffling apparatus of claim 11, wherein the muffling apparatus is attached to a first end of a support element, and wherein a second end of the support element is attached to the internal area of the oil separator. 